C. Cremaschini, J. C. Miller, M. Tessarotto
Astrophysical plasmas in accretion discs are usually treated in the framework
of fluid or MHD approaches but there are some situations where these treatments
become inadequate and one needs to revert to the more fundamental underlying
kinetic theory. This occurs when the plasma becomes effectively collisionless
or weakly-collisional such as, for example, in radiatively inefficient
accretion flows onto black holes. In this paper, we lay down the basics of
kinetic theory in these contexts. In particular, we formulate the kinetic
theory for quasi-stationary collisionless accretion disc plasmas in the
framework of a Vlasov-Maxwell description, taking the plasma to be
non-relativistic, axisymmetric, gravitationally-bound and subject to
electromagnetic fields. Quasi-stationary solutions for the kinetic distribution
functions are constructed which are shown to admit temperature anisotropies.
The physical implications of the theory are then investigated and the equations
of state and angular momentum conservation law are discussed. Analysis of the
Ampere equation reveals the existence of a quasi-stationary kinetic dynamo
which gives rise to self-generation of poloidal and azimuthal magnetic fields
and operates even in the absence of turbulence and/or instability phenomena.
View original:
http://arxiv.org/abs/1201.1838
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